Motor-driven hoist with protective braking system

ABSTRACT

A motor driven hoist especially useful for moving nuclear reactor fuel is described. A principal feature is a positive locking system to prevent load dropping when a malfunction develops. The hoist includes a main drum-supporting cable for the load and which is directly driven by a main hoist motor. A worm wheel is coupled to the drum. A mating worm is in turn driven by an auxiliary motor which has insufficient power to carry the load. The drum cannot rotate unless both motors are operative. The auxiliary worm motor and worm gearing function as an automatic lock which opens to permit drum rotation only so long as the main motor is delivering power to the main drum. Additional features include directly driven auxiliary drums for simultaneously supplying electrical or air hoses to the load, and means for translating the drum while rotating same to maintain the drum cable aligned with the load.

United States Patent Jones MOTOR-DRIVEN HOIST WITH PROTECTIVE BRAKING SYSTEM 7 ABSTRACT Inventor: Cecil Roy Jones, Orange, Calif.

A motor dr1ven ho1st especially useful for movmg nu- Asslgneei Transfer Systems Incorporated, clear reactor fuel is described. A principal feature is a North Haven, Connpositive locking system to prevent load dropping when [22] Filed: June 23 1972 a malfunction develops. The hoist includes a main drum-supporting cable for the load and which is di- PP N05 265,571 rectly driven by a main hoist motor. A worm wheel is coupled to the drum. A mating worm is in turn driven 52 US. Cl. 254/ 254/ 254/ B by an auxiliary which has ihsufhcieht POWer 51 1111. C1 B66d 5/18 Carry the load- The rotate unless both [58] Field 61 Search 254/180 186 169 170- motors are hperahve- The auxiliary Worm and 245/84 4 worm gearing function as an automatic lock which opens to permit drum rotation only so long as the [56] References Cited main motor is delivering power to the main drum. Ad-

ditional features include directly driven auxiliary UNITED STATES PATENTS drums for simultaneously supplying electrical or air 117811134 11/1930 Shoemaker 242/158 R hoses to the load, and means for translating the drum g f 'x i while rotating same to maintain the drum cable 3:477:695 11/1969 Noly 254 150 filgs the load- 3,54l,888 11/1970 Hegar 254/170 Primary ExaminerRobert J. Spar 11 Claims, 4 Drawing Figures Assistant Examinerl(enneth Noland MAIN MOTOR 21 10 u, HOIST GEAR DRUM Q 45 2 40 29 ffff Iii Ti 45 33 35 Q Q Q i \YY\\Y MOTOR-DRIVEN HOIST WITH PROTECTIVE BRAKING SYSTEM This invention relates to a motor-driven hoist provided with a positive locking system to protect against load dropping when a power failure develops. It is especially adapted for moving nuclear reactor fuel.

Power-generating nuclear reactor stations frequently require the replacement or rearrangement of its radioactive fuel elements for highest efficiency. For this purpose, a grapple is lowered from an overlying refueling platform into the reactor well to couple to the fuel element, which is underwater, and then the fuel element hoisted out of the reactor core and placed in a new core position or moved into an adjacent fuel storage pool. It is important both for safety reasons and to avoid cumbersome decontamination procedures to prevent dropping of the fuel load should a power failure develop. Conventional hoists are often provided with dual braking systems to satisfy the foregoing requirement. A typical system has the hoist motor driving a worm gear which in turn drives the cable drum. The worm gearing is irreversible and thus if the motor fails, the worm gearing cannot be reverse driven and locks. A second braking system is provided by a disc brake connected to the drum shaft opposite to the motor. The brake is kept open by air pressure to a spring-loaded cylinder. Interruption of power opens an electrical solenoid, which vents the air pressure causing the spring to activate the brake.

There are several disadvantages of the foregoing system. Driving the drum through the worm gearing, which has a low efficiency, produces a large energy loss thus requiring a large electrical motor. Another disadvantage is that the overall dimensions of the system and its total weight are excessive. In addition, since the braking devices are coupled by way of the drum shaft, a malfunction at the shaft or drum can cause load dropping without protective braking. Still further, to provide an air hose or electrical cable to the load, which is often required for underwater grappling of fuel, requires separate reels and mechanisms to maintain the cabling taut. Furthermore, since the unwinding cable moves across the drum, to avoid a large angle formed between the cable when at opposite drum ends and the cable idler sheave, which is undesirable, a further enlargement of the required space becomes necessary.

A principal object of the invention is a hoist provided with a safety braking system which is continuously operative to protect against load dropping throughout a wider range of possible malfunctions than was heretofore available.

Another object of the invention is a hoist system utilizing a drum-supported cable and providing a safety braking system which operates directly off the drum.

Still a further object is a hoist system combined with safety brake which incorporates auxiliary drums for supplying auxiliary cabling or hosing to the load.

Still another object is an improved hoist system with safety brake of reduced size and weight.

These and other objects of the invention as will appear hereinafter are achieved, in accordance with the invention, by utilizing the worm drive principle but without sacrificing gearing efficiency. In the invention, the main cable drum is driven directly by a main electrical motor. Coupled to the drum is worm gearing driven in turn by a smaller auxiliary electrical motor motor functions to maintain this second brake unlocked so long as the main hoist motor is operative. Should the latter fail, the worm gear motor cannot drive the drum and the brake is locked. Since the main drum is not directly driven through the worm, gearing losses are kept low.

As further features of the invention, additional drums are provided which are driven off of the main drum and can be used to simultaneously supply additional cabling or hosing to the main cable load. Still further, the entire system of main motor, main drum, auxiliary drums, and worm gearing and its auxiliary motor, are mounted for translation simultaneously with main drum rotation to maintain the depending cables without the necessity of additional sheaving aligned with the load.

One embodiment of the invention, by way of example, will now be described in greater detail with reference to the accompanying drawing, wherein:

FIG. 1 is an elevational side view of one form of hoisting apparatus in accordance with the invention;

FIG. 2 is a partly cross-sectional, partly elevational side view of the hoist illustrated in FIG. 1, on an enlarged scale;

FIG. 3 is a partly cross-sectional, partly elevational end view of the hoist illustrated in FIG. 1, on a scale approximately the same as that of FIG. 2;

FIG. 4 is a diagrammatic detail view, also enlarged, illustrating the flexible coupling between the main and auxiliary drums.

Referring now to the drawings, the conventional reactor power station includes a reactor well containing within an underwater core assemblies of radioactive fuel elements, typically in the form of elongated configurations. On the reactor floor is provided a movable refuelling platform or bridge, which can be positioned over a particular fuel assembly. On the platform is mounted a hoist connected to a grapple, by means of which a fuel assembly underwater can be gripped and lifted out of the core and moved to a different core position or to an adjacent fuel storage pool. Safety standards demand that the hoist be provided with adequate braking mechanisms to prevent dropping of the fuel load during the moving procedure should a malfunction arise in the hoist mechanism.

One form of hoisting apparatus capable of satisfying the stringent safety standards established in the nuclear reactor field is illustrated in FIGS. 1-3. It comprises what is essentially a conventional electrically operated winch hoist which has been modified to incorporate a novel braking system, additional hose or cable supply drums, and provision for translating the system to align the unwinding cables with the load.

The conventional part of the hoist, which is commercially available, comprises a main electrical motor 10 whose motor shaft (not shown) extends through a main or load cable drum 20 to a conventional reducing gear box 12 employing for example normal high-efficiency spur gearing. The output of the reducing gears is directly coupled to a driving gear (not shown) on the right end of the main drum 20. Also included is a normal braking system 13, which can be of the disc brake type, coupled to the main motor shaft or drum and adapted to brake the drum or load whenever electrical power is interrupted, but this primary brake construction 13 as such is well known and further details of its interior construction are unnecessary and are omitted. Any known braking system capable of supporting the load when the main hoist motor is stopped can be employed.

The second braking system in accordance with the invention is afforded by irreversible gearing, specifically worm gearing, coupled to the left side of the drum. In particular, the main cable drum has a spur gear 21 mounted on its left side. Coupled to the spur gear 21 is a mating gear 22 rigidly mounted on an elongated hollow shaft 23 journalled in main load bearings 24 at opposite shaft ends. The shaft bearings 24 are supported on a platform 25 having end uprights 26 and a supporting base 27. Extending through the hollow shaft is a threaded lead screw 30, whose ends are supported by end uprights 31 connected to a main support base member 32. The lead screw is fixed in position and cannot rotate, but the hollow shaft 23 is free to rotate about the lead screw 30. In engagement with the left end of the lead screw is a lead-screw nut 33 which is fixed to the hollow shaft 23. Mounted on the hollow shaft and rotatable therewith is a worm wheel 35. Also attached to the shaft platform 25 is a support 36 for an auxiliary electrical motor 37 whose shaft 28 is connected to a worm 38 in engagement with the worm wheel 35. The worm 38 is journalled in bearings 39 mounted on the platform 36 (FIG. 3). Electrical connections 40 are made to the main load motor 10, and also 41 to the auxiliary motor 37. Both connections 40, 41 then go to a suitable controller of a conventional type for controlling the speed and direction of rotation of the motors in order to wind or unwind a main load cable 45 in order to raise or lower, respectively, the load. As will be noted, both motors are electrically connected together so that when power is supplied to cause the main motor 10 to rotate in a particular direction, simultaneously power is also supplied to the auxiliary motor 37 to cause its rotation in a particular direction, specifically, the same direction that the worm 38 would rotate when the main motor 10 is driven, if the auxiliary motor 37 were not present and high friction did not prevent reverse driving of the worm 38.

The operation is based on the following. There is a direct coupling of the main drum 20 to the worm 38 via the spur gearing 21, 22 and worm wheel 35. The friction losses that develop in trying to rotate the worm 38 by driving its mating worm wheel are so high that the worm 38 cannot be reversely driven for all practical purposes, and hence the main drum 20 will be locked in position by the worm gear 38 and will not be moved (in the absence of the primary brake 13). Thus, in the absence of the auxiliary motor 37 (and the primary brake 13), the main motor 10 cannot move a load on the cable 45. What the auxiliary motor 37 does is to drive the worm 38 in the same direction it would tend to rotate if the main motor 10 could drive it, and thus in effect maintains the secondary worm gear brake unlocked and allows the main drum 20 to be rotated by the main motor 10. However, the auxiliary motor 37, which is of the known torque type, is chosen to have insufficient power to drive the load through the worm gearing 38, 35. Hence, if the main motor 10 fails, the load will lock since it cannot be driven by the auxiliary motor 37 and it cannot reverse drive the worm 38. As

a result, for the load to be moved, the main motor 10 must be applying power to the main drum 20, and as a second requirement the auxiliary motor 37 must be applying power to the worm 38 tending to cause it to rotate, to allow the main drum in turn to rotate. The primary braking system 13 functions to support the load whenever the main hoist motor power is interrupted,

thus, during normal operation whenever the main motor 10 is stopped. This third essential prevents the load during normal operation from being transmitted to the worm 38. Once the worm 38 is loaded, the power of the auxiliary motor 37 is insufficient to raise the load, and other means has to be employed to raise or lower the load to unload the worm. Achievement of activation of the primary brake before the secondary brake (with no malfunction) is readily accomplished in known ways, for example, by adjustment of the clearance between the teeth of the worm 38 and worm wheel 35. Of course, if the primary braking system 13 malfunctions and cannot support the load, then the load is transmitted to and arrested by the secondary worm brake which is sized to handle the full load. Any malfunction in this system which prevents or interferes with these three essential requirements prevents load movement.

When everything is in order and the worm wheel 35 is rotated, this causes rotation of the hollow shaft 23 and the nut 33 fixed thereto, which causes translation of the nut 33 and the hollow shaft 23 fixed thereto. This in turn translates the platform support 25 for the ho]- low shaft, and all other members supported thereby, which includes the main drum 20 and main motor 10 also via upright extensions 29. As will be observed in FIG. 2, the load cable 45 is wound around the main drum 20 in suitable grooves therein and then depends from the drum 20 passing behind the platform 27 and extending down through an opening in the base support 32 to terminate in a suitable load support member (not shown). For moving fuel, typically the hoist cable extends within and operates a series of telescoping tubes (not shown) known as a grapple, and terminating in a suitable structure for locking to the fuel. If the drum 20 were fixed in lateral position, as the load cable 45 unwound it would laterally shift relative to the location'of the load. By means of this feature of the inven tion, the drum 20 translates to the right of FIG. 2 while it rotates so that the unwinding cable maintains a fixed position relative to the hole 50 in the base plate 32 and thus to the load. When the cable 45 is rewound on the main drum, then the platform and other members translates to the left of FIG. 2.

The platform 25 is supported on the main support 32 by means of linear bearings 51 on a pair of spaced shafts 52 that allow free sliding movement of the bearings and platform along the shafts in the manner described above.

Mounted on the hollow shaft 23 is a first auxiliary drum 55 by way of bearings 56 which permit free rotation thereof about the hollow shaft. The auxiliary drum 55 is driven by a flexible coupling 57 via the hollow shaft. In one form, a suitable member 58 is secured to the hollow shaft 23, and another member 59 is secured to the inside of the drum, and these two members are coupled by way of a tight spring 60 (See also FIG. 4). The spring tension is such as to cause the first auxiliary drum 55 to rotate in a direction which will rewind its cable 61, which may be an electrical cable or an air hose. This auxiliary drum cable is often required to supply air pressure or electrical power to the fuel grapple to operate same. As the hollow shaft 23 is rotated in conjunction with the main drum, the arrangement is such that the auxiliary drum 55 follows the main drum and winds or unwinds its auxiliary cable 61 at the 4 same rate as that of the load cable 45, thus enabling the auxiliary cable to be connected to the load and to follow along with it. The flexible coupling 57 providing a winding tension on the auxiliary drum ensures that the auxiliary cable remains taut so as not to interfere with handling of the load.

FIG. 3 also shows if needed the provision of a second auxiliary drum 65 mounted on a shaft 80 supported on the platform and activated by spur gearing 68 coupled to the spur gear 22 on the hollow shaft 23. This second drum 65 will thus rotate and translate in synchronism with the first auxiliary drum 55 and can be used to supply a second cable 82 or hose to the load. To keep the main load cable and auxiliary cables near one another, a suitable idler sheave 70 is mounted as schematically indicated at 71 on the bottom base support 32 to bring the cable 61 that comes off of the right hand side of the first auxiliary drum 52 (FIG. 3) over to the load cable 45. As an alternative, the second auxiliary drum 65 can be driven by suitable gearing from the first auxiliary drum 52, thereby incorporating the cable taut feature described in connection with FIG. 4.

As shown in FIG. 3, the worm gear 38 is provided with a square shank end 72 which projects beyond its bearing 39. In an emergency, this shank 72 can be utilized for hand driving of the worm 38 in order to raise or lower the load in case of failure of the electrical power supply or to release the worm.

As has thus been described, a hoist with safety brake is obtained featuring two separate and independent braking systems, the static worm gearing and the usual hoist load brake, affording excellent protection against a wider range of possible hoist malfunctions, all the while maintaining small size and low weight, and high efficiency thus enabling reduced driving power.

While my invention has been described in connection with specific embodiments thereof, those skilled in the art will recognize that various modifications are possible within the principles enunciated herein and thus the present invention is not to be limited to the specific embodiments disclosed.

What is claimed is:

l. Hoisting apparatus especially adapted for moving a load such as nuclear fuel, comprising a main drum, a load cable wound on the drum for coupling to the load, main drive means directly coupled to the main drum for driving same, substantially irreversible gearing separate from the main drive means, means for continuously engaging said irreversible gearing to the main drum, auxiliary drive means connected to the irreversible gearing for driving same in the same direction as that imparted to the irreversible gearing by the main drum when the latter is driven by the main drive means, and means for activating the auxiliary drive means whenever the main drive means is activated.

2. Hoisting apparatus as claimed in claim I wherein the main drive means is an electrical motor capable of driving the main drum with the load cable coupled to the load, and the auxiliary drive means is a separate electrical motor incapable alone or driving the main drum with a loaded load cable.

3. Hoisting apparatus as set forth in claim 2 wherein the irreversible gearing comprises a worm wheel directly coupled to the main drum and a worm mating with the worm wheel and directly coupled to the auxiliary motor.

4. Hoisting apparatus as claimed in claim 3 and further comprising a support, a platform on said support and translatable relative thereto, said motors, drum and gearing being mounted on said platform, and means in response to drum rotation to translate said platform.

5. Hoisting apparatus as set forth in claim 4 and further comprising a lead screw, threaded means in engagement with said lead screw, means coupling said platform to said threaded means, and means coupling said threaded means to said main drum for causing rotation of the threaded means in response to drum rotation.

6. Hoisting apparatus as claimed in claim 1 and further comprising at least one auxiliary drum, at least one hose or auxiliary cable wound on the auxiliary drum, and means for rotating the auxiliary drum in response to rotation of the main drum.

7. Hoisting apparatus as claimed in claim 6 wherein the rotating means for the auxiliary drum includes a flexible coupling in order to maintain taut the hose or auxiliary cable relative to the load.

8. Hoisting apparatus as claimed in claim I wherein the irreversible gearing is a secondary brake, and further comprising a primary brake coupled to the main drum and adapted to support the load whenever power to the main drive means is interrupted.

9. Hoisting apparatus especially adapted for moving a load such as nuclear fuel, comprising a main drum, a load cable wound on the drum for coupling to the load, high efficiency main drive means directly coupled to the main drum for driving same, substantially irreversible gearing separate from the main drive means and comprising a worm wheel directly coupled to the main drum and a worm mating with the worm wheel, separate auxiliary drive means directly coupled to the worm for driving the irreversible gearing in the same direction as that imparted to the irreversible gearing by the main drum when the latter is driven by the main drive means,

means for activating the main drive means both to wind and unwind the load cable, and means for activating the auxiliary drive means whenever the main drive means is activated, said auxiliary drive means being incapable alone of driving the main drum with a loaded load cable but being capable of maintaining the irreversible gearing in an unlocked condition in the absence of malfunction within the apparatus. 10. Hoisting apparatus especially adapted for moving a load such as nuclear fuel, comprising a main rotatable drum, a load cable wound on the drum for coupling to the load, main drive means directly coupled to the main drum for driving same, substantially irreversible gearing directly and continuously coupled to the main drum and tending to lock the drum and prevent drum rotation both during winding and unwinding of the load cable; and means for maintaining the irreversible gearing in an unlocked condition in the absence of an apparatus malfunction, said last-named means including auxiliary drive means connected to the irreversible gearing further comprising a separate braking system coupled to the main drum and adapted to support the load whenever power to the main drive means is inter- 

1. Hoisting apparatus especially adapted for moving a load such as nuclear fuel, comprising a main drum, a load cable wound on the drum for coupling to the load, main drive means directly coupled to the main drum for driving same, substantially irreversible gearing separate from the main drive means, means for continuously engaging said irreversible gearing to the main drum, auxiliary drive means connected to the irreversible gearing for driving same in the same direction as that imparted to the irreversible gearing by the main drum when the latter is driven by the main drive means, and means for activating the auxiliary drive means whenever the main drive means is activated.
 2. Hoisting apparatus as claimed in claim 1 wherein the main drive means is an electrical motor capable of driving the main drum with the load cable coupled to the load, and the auxiliary drive means is a separate electrical motor incapable alone or driving the main drum with a loaded load cable.
 3. Hoisting apparatus as set forth in claim 2 wherein the irreversible gearing comprises a worm wheel directly coupled to the main drum and a worm mating with the worm wheel and directly coupled to the auxiliary motor.
 4. Hoisting apparatus as claimed in claim 3 and further comprising a support, a platform on said support and translatable relative thereto, said motors, drum and gearing being mounted on said platform, and means in response to drum rotation to translate said platform.
 5. Hoisting apparatus as set forth in claim 4 and further comprising a lead screw, threaded means in engagement with said lead screw, means coupling said platform to said threaded means, and means coupling said threaded means to said main drum for causing rotation of the threaded means in response to drum rotation.
 6. Hoisting apparatus as claimed in claim 1 and further comprising at least one auxiliary drum, at least one hose or auxiliary cable wound on the auxiliary drum, and means for rotating the auxiliary drum in response to rotation of the main drum.
 7. Hoisting apparatus as claimed in claim 6 wherein the rotating means for the auxiliary drum includes a flexible coUpling in order to maintain taut the hose or auxiliary cable relative to the load.
 8. Hoisting apparatus as claimed in claim 1 wherein the irreversible gearing is a secondary brake, and further comprising a primary brake coupled to the main drum and adapted to support the load whenever power to the main drive means is interrupted.
 9. Hoisting apparatus especially adapted for moving a load such as nuclear fuel, comprising a main drum, a load cable wound on the drum for coupling to the load, high efficiency main drive means directly coupled to the main drum for driving same, substantially irreversible gearing separate from the main drive means and comprising a worm wheel directly coupled to the main drum and a worm mating with the worm wheel, separate auxiliary drive means directly coupled to the worm for driving the irreversible gearing in the same direction as that imparted to the irreversible gearing by the main drum when the latter is driven by the main drive means, means for activating the main drive means both to wind and unwind the load cable, and means for activating the auxiliary drive means whenever the main drive means is activated, said auxiliary drive means being incapable alone of driving the main drum with a loaded load cable but being capable of maintaining the irreversible gearing in an unlocked condition in the absence of malfunction within the apparatus.
 10. Hoisting apparatus especially adapted for moving a load such as nuclear fuel, comprising a main rotatable drum, a load cable wound on the drum for coupling to the load, main drive means directly coupled to the main drum for driving same, substantially irreversible gearing directly and continuously coupled to the main drum and tending to lock the drum and prevent drum rotation both during winding and unwinding of the load cable; and means for maintaining the irreversible gearing in an unlocked condition in the absence of an apparatus malfunction, said last-named means including auxiliary drive means connected to the irreversible gearing for driving same in the same direction as that imparted to the irreversible gearing by the main drum when the latter is driven by the main drive means, and means for activating the auxiliary drive means during winding and unwinding of the load cable.
 11. Hoisting apparatus as claimed in claim 10 and further comprising a separate braking system coupled to the main drum and adapted to support the load whenever power to the main drive means is interrupted. 